This invention relates to an arrangement for protecting an air pump used to generate air bubbles in a central liquid filled tube of an article display case from damage caused by the back-up of liquid from the tube into the pump when the pump is in a de-energized condition.
Broadly speaking, article display cases having an elongated, vertically extending, transparent, central tube filled with a liquid such as water in which air bubbles can be generated by means of a conventional high pressure air pump are old and well known in the art. Typically, such a central tube is mounted on the face of an electric lamp and the lamp is energized simultaneously with the air pump so that air bubbles formed in the liquid in a lower end of the tube will be illuminated as they rise through the tube. An upper end of the tube is capped or otherwise enclosed but contains perforations therein through which the air bubbles can escape the liquid to ambient atmosphere, they being continuously replaced in the liquid by the air pump at the base of the tube.
Typically, a cone shaped cover surrounds a base portion of the tube and conceals the pump, an air line from the pump to a base portion of the tube, the lamp and other components of the bubble forming and illuminating system from view. Usually, a number of vertically spaced apart, clear plastic, article support plates are glued to and around the central tube. A colored lens may be used over the face of the lamp to cause a colored light beam to illuminate the bubbles in the tube in like color, thus making an attractive and eye catching display for candy and/or other articles placed for public exhibition on the support plates. An example of such a prior art display case is sold by Mirrotek International LLC., 90 Dayton Avenue, Passiac, N.J., 07055, under the registered trademark BUBBLE LAMPS as model No. LBB60SF.
One difficulty which has been encountered when using such prior art display cases is that liquid in the central tube has a tendency to back-up through the air line and severely damage, if not destroy, the air pump upon deactivation of the pump and expulsion of high pressure air from the air line. To overcome this problem in the prior art, a one way check valve has been placed in the air line between the pump and the tube which allows high pressure air to flow from the pump into the tube but which closes upon de-energizing the pump to prevent liquid from the tube from backing up through the air line past the check valve into the pump. The problem is that such check valves have a very short service life span as compared to the service life span of the usual air pump. Accordingly, such check valves eventually fail, usually sooner, rather than later, resulting in the loss of a relatively expensive air pump to moisture damage long prior to the end of its normally expected service life span.
To extend the effective life of the pump in such display cases, resort has been had to the placement of two or three such check valves in series in the air line between the pump and the tube, the theory being that if one such valve fails, the other one or two will continue to operate to protect the pump. Eventually, however, and usually long prior to the end of the useful service life of the pump under normal circumstances, all of the check valves in the series combination will fail resulting in moisture damage to the pump.
Another difficulty I have noticed with these prior art central tube display cases is that, because of their length, which is typically about five feet in height, they tend to be somewhat rickety, unstable and tiltable on their bases, sometimes to the point of actually toppling over, thus spilling articles from the plates and losing liquid from the upper end of the tube through the perforations therein. This is a particular problem where the display case is located in high traffic areas such as in busy retail stores and the like.
By means of my invention, these and other difficulties encountered using prior art display cases of the aforementioned type are substantially eliminated.